cerbero: Also support 'gir' as the introspection option
cerbero: Also support 'gir' as the introspection option

GNOME is moving to 'introspection' as the option, but many projects
are still using 'gir'.

nirbheek/cerbero,GStreamer/cerbero,fluendo/cerbero,nirbheek/cerbero,fluendo/cerbero,atsushieno/cerbero,atsushieno/cerbero,nirbheek/cerbero,GStreamer/cerbero,fluendo/cerbero,fluendo/cerbero,GStreamer/cerbero,GStreamer/cerbero,fluendo/cerbero,atsushieno/cerbero,GStreamer/cerbero,atsushieno/cerbero,nirbheek/cerbero,atsushieno/cerbero